EP2253968A2 - Testing device for ultrasound sensor, ultrasound measuring device and method for testing an ultrasound sensor - Google Patents

Abstract

The device has a connection element with a recess for a connector of an ultrasonic probe. The connection element directly or indirectly contacts a subset of signal lines in an electrical manner. A measuring unit automatically measures capacitance value detected at the contacted signal lines based on recharging time of the signal lines. A comparator compares the capacitance value with reference values, and a display unit displays detected errors. The measuring unit has a multiplexer e.g. 8-channel multiplexer, for sequential contacting of a part of the signal lines. An independent claim is also included for a method for testing an ultrasonic probe.

Description

The invention relates to a test device for an ultrasound probe, an ultrasound measuring device and a method for testing an ultrasound probe.

Ultrasonic measuring devices are used to examine objects, eg. As used for quality control, and in particular for medical purposes for the study of animal and human bodies. The ultrasonic waves used for the investigation are generated with piezoelectric crystals arranged in an ultrasonic probe. Reflected ultrasonic waves can also be detected again with these crystals. In particular, in systems for medical technology, a plurality of such crystals are usually arranged in the probe, which allow a planar or spatial information about the object under investigation. The individual crystals are each connected to a signal line. The regular monitoring of the functionality of an ultrasound device, in particular its probe, is essential because disturbances in the probe are not always detected by the operating personnel. Misdiagnoses that may be fatal to the patient being examined can not be ruled out in the event of a malfunction.

Apparatus and methods for testing ultrasound machines and their probes are known (see e.g. EP 1629779 B1 ). In this case, a test object is examined by means of the ultrasound device to be tested. Deviations from the result can then give indications of an existing error. However, test examinations with a separate test object are usually time-consuming and thus costly.

It is an object of the present invention to provide a test device, an ultrasound measuring device and a method for testing ultrasound probes, with which a reliable and simple function test of ultrasound probes is possible.

In a test device for an ultrasonic probe, this object is solved by the features of claim 1.

Furthermore, this object is achieved in an ultrasonic measuring device by the features of claim 4 and in a method for testing an ultrasonic probe by the features of claim 5.

The system signal line, piezoelectric crystal and plug connection can be considered as an electrical unit with a certain electrical capacity. Disruptions to this system, in particular a cable break in the signal line, a loss of contact or a short circuit usually lead to a change in the associated capacity. This fact makes use of the invention to reliably detect errors in the ultrasound probe.

The capacity can be determined in different ways. Since capacitances are always connected to an impedance, the capacitance may be e.g. be determined by the impedance. Although this method is basically simple, it has a low measuring range for the requirements concerned.

Furthermore, the capacity can be determined by means of an AC measuring bridge. Although this method involves a good measuring range, it is time-consuming, since the respective variable resistances for adjusting the bridge must be set for each measurement.

It is advantageous to determine the capacity by measuring the charging time. This procedure is generally known (see, for example, htt2: //www.klausrohwer.de/privat/hobbiesielektro/cmess/index.atm , as of 30.09.2008). If a capacitive component is connected to a constant current source, the voltage applied to the component changes linearly over time according to the formula $$U=\frac{I\cdot t}{C}$$

If one measures a voltage change over a certain time interval, the capacitance of the examined component can be determined from this. This time measurement can be z. B. perform well with a NE555 device. This timer contains two comparators that compare the input signal with their reference voltages, which are 1/3 and 2/3 of the supply voltage. The comparators set and reset the RS flip-flop contained in the NE555, which generates a square-wave signal. The square-wave signal has a high frequency in accordance with the dependence of the pulse duration t _end -t _start from the capacitance in the case of small capacitances and a correspondingly low frequency in the case of large capacitances. The ratio between pulse duration and capacitance is determined by the resistance R of the capacitive system, as shown below:

wobei U_vcc die Versorgungsspannung ist. Als Schaltschwellen für den NE555-Baustein sind 1/3 U_vcc und 2/3 U_vcc gesetzt. Hieraus resultieren die folgenden Formeln für die Spannungen zum Beginn und zum Ende der Impulsdauer. $$U\left(\mathit{Start}\right)=1/3\mathit{Uvcc}$$

$$U\left(\mathit{Ende}\right)=2/3\mathit{Uvcc}$$

The charging of a capacity takes place exponentially according to the formula $$U\left(t\right)=\mathit{Uvcc}\cdot \left(1-{\mathrm{e}}^{\frac{-t}{\left(R\cdot \mathit{cx}\right)}}\right)$$

where U _{vcc is} the supply voltage. The switching thresholds for the NE555 module are set to 1/3 U _vcc and 2/3 U _vcc . This results in the following formulas for the voltages at the beginning and at the end of the pulse duration. $$U\left(\mathit{begin}\right)=1/3\mathit{Uvcc}$$

$$U\left(\mathit{The\; End}\right)=2/3\mathit{Uvcc}$$

From this, by substituting the above formula and equivalent conversions, the following formula for the capacity is given as a function of the ratio of the pulse duration to the resistance. $$C_X=\frac{\left({\mathrm{t}}_{\mathrm{The\; End}}\mathrm{-}{\mathrm{t}}_{\mathrm{begin}}\right)}{\mathrm{R}\mathrm{\cdot }\ln \left(\mathrm{2}\right)}$$

If the capacitance determined during the test measurement deviates from a previously determined desired value, it is possible to conclude that damage has occurred within the ultrasound probe. The resolution of the test apparatus can be improved by increasing the resistance R of the system so that a longer time is available for measuring for the same capacitance.

The nominal value of the capacitances of the individual signal lines can be specified by the manufacturer of the ultrasound probe. Alternatively, the target capacities are determined with the test device according to the invention by means of correctly functioning ultrasound probes of a specific type.

With suitable measurement resolution, it is possible to determine whether a detected damage in the area of the connector, along the signal cable, in the area of the probe kink protection or in the probe element itself is given. In particular, in the case of a cable break, it is possible to accurately determine the location of the defect in the signal cable to a few centimeters, since the capacity of the system under test is correspondingly reduced. In addition to a cable break, a short circuit, that is, an unwanted electrical connection, e.g. between adjacent signal cables. This results in a test measurement to an excessive capacity.

Using a separate test device, ultrasonic probes can be tested by simply placing the plug of the probe on the corresponding connection element of the test device.

If the probe type is known, an automated test run can be carried out in which the applied capacitance is determined for each signal line examined and compared with a setpoint value. A display unit then indicates to the user if the ultrasound probe is functioning properly or if there is an error. As a rule, the nature of the fault as well as the location of the fault can also be specified, which makes it easier to repair the device. In order to be able to measure through the multiplicity of signal lines, for example 128, multiplexers are used, for example sixteen 8-channel multiplexers.

Such a test device can also already be part of an ultrasound measuring device. Thus, in the ultrasound measuring device, it would be possible by default to specify via an electronic timetable to perform a test measurement at specific times. The times can be given on a calendar basis or depending on the usage, eg. For example, before each measurement, immediately after each time the instrument is switched on, or before every 20th measurement. The test measurement can then be started automatically or the operator is reminded by an ad to start the test run.

Claims (6)

Test device for an ultrasonic probe, wherein the ultrasonic probe has a plurality of signal lines, comprising a) a connection element with a receptacle for a plug of the ultrasound probe, wherein the connection element electrically or indirectly contacts at least a subset of the signal lines, b) a measuring unit for automated measurement of the detectable at the respective contacted signal line capacitance, c) means for comparing the ascertained capacity values with target values, as well as d) a display unit for displaying a detected error. Test device according to claim 1, characterized in that the measuring unit has at least one multiplexer for the sequential contacting of at least a part of the signal lines. Test device according to claim 1 or 2, characterized in that the measuring unit is suitable for determining the capacity on the basis of the charging time of the signal line to be examined. Ultrasonic measuring device, characterized in that it comprises a test device according to claims 1 to 3. A method of testing an ultrasound probe having a plurality of signal leads, wherein at least a portion of the signal leads of the ultrasound probe electrically contact, verify the capacitance of each contacted signal lead and compare it to a nominal value of the capacitance. A method according to claim 5, characterized in that the measurement of the capacitance takes place on the basis of the charging time of the signal line to be examined.